This invention is directed to a microelectromechanical structure (MEMS), and particularly to an electrically isolated, mechanically anchored metal MEMS beam for use in a microactuator, such as a microactuator for fine positioning a slider relative to a disc in a disc drive.
Microactuators are employed in a wide variety of applications for controlling the motion of microstructures, including switches, variable impedances, etc., as well as for positioning microstructures such as head/slider structures relative to a selected track on a disc in a disc drive. For example, as track density becomes increasingly greater in disc drives, the track width and spacing becomes increasingly smaller, necessitating more accurate control of the micro positioning of the slider to the tracks. The slider is supported by an actuator arm that is controlled by a voice coil motor to coarsely position the slider relative to a track. The microactuator is carried on the arm to finely position the slider relative to the track.
A typical microactuator in a disc drive employs a stator and a rotor, with the slider mounted to the rotor. The slider, which carries the transducing head, is typically aerodynamically designed to xe2x80x9cflyxe2x80x9d a small distance above the surface of the confronting disc. The stator is supported by the actuator arm and is usually preloaded by a load beam that contributes to the control of the fly height of the slider.
Where the microactuator provides a linear motion to the rotor, suspension beams between the stator and rotor may be nearly as long as the entire microactuator. The long length to the suspension beams usually allows the beams to be correspondingly wide, yet still retain the required flex characteristics to permit movement between the stator and rotor. The width of the suspension beams in linear microactuators is usually great enough to permit formation of a metal conductor in a trench in the beam for connection to the rotor and the head. However, rotary microactuators employ suspension beams that are splayed out in a pattern similar to spokes on a wheel. Consequently, the beams are shorter than suspension beams in linear microactuators, requiring the beams to also be more narrow to retain the required flex characteristics. For example, the width of a suspension beam in a rotary microactuator is often less than about 10 microns (xcexcm). As a result, it is not practical to form a trench in the beam for support of the beam. While this feature would seemingly dictate use of linear microactuators, rotary microactuators have the desirable feature of rejection of the voice coil motor acceleration.
To operate the head it is necessary to provide electrical connections between the stator and the rotor. In most disc drives, a flex circuit consisting of flexible conductive wires, is supported by the actuator arm and is connected to conductive pads on the stator and on the rotor and slider to operate the microactuator and supply write signals to, and read signals from, the head. However, the small rigidity of the flex circuit connection to the rotor and slider adversely affects operation of the microactuator. The present invention provides a solution to this and other problems, and offers other advantages over the prior art.
The present invention is directed to a metal suspension beam for a microactuator that provides electrical connection between the stator and rotor of the microactuator, that is electrically isolated from the stator and rotor and that provides mechanical support for the rotor and its load. As used herein, xe2x80x9cstatorxe2x80x9d refers to the portion of the microactuator that is primarily supported by a structure external to the microactuator. Hence, the stator may be rigidly mounted to the actuator arm of a disc drive and is movable with that arm. xe2x80x9cRotorxe2x80x9d refers to the portion of the microactuator that is primarily supported by the stator and is movable relative to the stator. The term xe2x80x9crotorxe2x80x9d is intended to be broadly construed, and should not be construed as limited to a particular type of motion. Hence, the rotor may move in a linear, rotary, or tortuous motion relative to the stator.
In one embodiment, a suspension beam is formed between a stator and a rotor of a microactuator. The stator and rotor regions are defined on a wafer, and isolation barriers are formed through the wafer in the stator and rotor regions. The isolation barriers define respective isolation regions in the respective stator and rotor regions. A conductive suspension beam is formed through the wafer between the first and second isolation regions. The wafer material between the stator and rotor regions is removed to form the stator and rotor.
In some embodiments, the isolation barriers are formed by forming isolation trenches through the wafer in the stator and rotor regions, and filling the first and second isolation trenches with insulation material. In other embodiments, the suspension beam is formed by forming a beam trench through the wafer between two isolation regions, and filling the beam trench with conductive material.
In other embodiments, conductive patterns are printed on a surface of the wafer material of the stator and rotor coupled to the suspension beam in the respective isolation regions.
In one embodiment, a microactuator includes a stator, a rotor supporting a load device, such as a slider, and suspension means is coupled to the stator and rotor to support the rotor and load device and provide electrical connection between the stator and rotor. In preferred embodiments, the suspension means comprises a metal beam, isolation regions on the stator and rotor supporting respective ends of the metal beam, insulation layers on the stator and rotor outside the isolation regions, and conductive traces supported on the insulation layers and coupled to the end of the metal beam in the respective isolation region.